win32: _platform/win32: add support for win32aevri/platform_win32

Copy the approach of 'Darwin' and provide a SandboxDummy.

This enables us to run 'bst workspace list' on Windows.

2 files changed, 63 insertions, 0 deletions

diff --git a/src/buildstream/_platform/platform.py b/src/buildstream/_platform/platform.py
index 11c9217be..af49b9e82 100644
--- a/src/buildstream/_platform/platform.py
+++ b/src/buildstream/_platform/platform.py
@@ -98,6 +98,8 @@ class Platform():
             backend = 'darwin'
         elif sys.platform.startswith('linux'):
             backend = 'linux'
+        elif sys.platform == 'win32':
+            backend = 'win32'
         else:
             backend = 'fallback'
 
@@ -105,6 +107,8 @@ class Platform():
             from .linux import Linux as PlatformImpl  # pylint: disable=cyclic-import
         elif backend == 'darwin':
             from .darwin import Darwin as PlatformImpl  # pylint: disable=cyclic-import
+        elif backend == 'win32':
+            from .win32 import Win32 as PlatformImpl  # pylint: disable=cyclic-import
         elif backend == 'fallback':
             from .fallback import Fallback as PlatformImpl  # pylint: disable=cyclic-import
         else:
diff --git a/src/buildstream/_platform/win32.py b/src/buildstream/_platform/win32.py
new file mode 100644
index 000000000..36680019d
--- /dev/null
+++ b/src/buildstream/_platform/win32.py
@@ -0,0 +1,59 @@
+#
+#  Copyright (C) 2019 Bloomberg Finance LP
+#
+#  This program is free software; you can redistribute it and/or
+#  modify it under the terms of the GNU Lesser General Public
+#  License as published by the Free Software Foundation; either
+#  version 2 of the License, or (at your option) any later version.
+#
+#  This library is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	 See the GNU
+#  Lesser General Public License for more details.
+#
+#  You should have received a copy of the GNU Lesser General Public
+#  License along with this library. If not, see <http://www.gnu.org/licenses/>.
+
+from ..sandbox import SandboxDummy
+
+from .platform import Platform
+
+
+class Win32(Platform):
+
+    def maximize_open_file_limit(self):
+        # Note that on Windows, we don't have the 'resource' module to help us
+        # configure open file limits.
+        #
+        # 'psutil' provides an rlimit implementation that is only available on
+        # Linux, as of version 5.3.
+        #
+        # Given that this limit is only important for SafeHardLinks FUSE, and
+        # we don't have FUSE on Windows, this won't be an obstacle for now.
+        #
+        # If it does turn out to be an obstacle, beware that the Windows API
+        # `_setmaxstdio` for increasing the open file limit only applies to the
+        # 'stream I/O level', i.e. `fopen()` and friends. CPython opens files
+        # using `_wopen()`, which is at the 'low I/O level'.
+        #
+        # You can see this in the function `os_open_impl` in `posixmodule.c` in
+        # CPython version 3.9.
+        #
+        # For more information:
+        # https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/setmaxstdio
+        #
+        pass
+
+    @staticmethod
+    def _check_dummy_sandbox_config(config):
+        return True
+
+    @staticmethod
+    def _create_dummy_sandbox(*args, **kwargs):
+        kwargs['dummy_reason'] = "There are no supported sandbox technologies for Win32 at this time."
+        return SandboxDummy(*args, **kwargs)
+
+    def _setup_dummy_sandbox(self):
+        self.check_sandbox_config = Win32._check_dummy_sandbox_config
+        self.create_sandbox = Win32._create_dummy_sandbox
+        return True